Method for eliminating instability in a vehicle automatic transmission which constantly shifts from one speed ratio to the higher ratio and conversely

ABSTRACT

The method for eliminating an oscillation phenomenon in a motor vehicle with an automatic transmission system. The mass of the vehicle is determined on the basis of the measured speed, the current ratio of the transmission, the engine speed and the opening angle of the engine throttle. The acceleration of the vehicle and a higher ratio is predicted from the mass of the vehicle. The total amount of tractive resistance applied to the vehicle is determined. The probability that there will be an oscillation phenomenon at a higher ratio termed &#34;oscillation risk&#34; is determined from the acceleration and tractive resistance information. A signal for preventing shifting to the higher ratio is generated from the oscillation risk information, with the signal being adapted to be applied to a transmission control device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention concerns a method of elimination of the phenomenon ofpumping of a motor vehicle with automatic transmission, as well as amotor vehicle employing that method.

2. Discussion of the Background

The pumping phenomenon is common in the field of motor vehicles withautomatic transmission. It involves an instability of the automatictransmission, which in some circumstances changes constantly from oneratio to the higher ratio and vice versa.

This phenomenon generally occurs when a vehicle equipped with anautomatic transmission is subjected to a certain level of resistantforces caused, in practice, by a sloping road, a presence of very strongwind, a sizable load of the vehicle, or even when the vehicle istraveling at a high altitude, that is, under relatively weak atmosphericpressures.

A theoretical solution to this problem consists in preventing any shiftto the higher gear ratio if the acceleration of the vehicle on thathigher ratio would be negative, and if the vehicle is subjected tostrong resistant forces.

A partial solution to the pumping problem was introduced, in practice,by the method of adaptive scheduling of shifting down, described inpatent U.S. Pat. No. 5,241,476 of the Chrysler Corporation. According tothat document, the method consists in determining whether the vehiclecould maintain its speed on the higher ratio and, if not, preventing theshift from the higher ratio. That method resorts to the calculation ofacceleration of the vehicle on the higher ratio, but without preciselyknowing the weight of the vehicle. The result of the determination istherefore erroneous. Furthermore, according to that document, only casesof pumping between third and fourth gear are eliminated, while the othercases of pumping can occur.

In addition, this method consists in locking the ratio engaged if thecalculations lead to an acceleration that would be negative on thehigher ratio. That criterion leads to untimely lockings on the ratioengaged, once the acceleration value calculated is slightly negative.Likewise, if acceleration ranges around zero, it would be randomlyswitched from a nonlocking condition to a locking condition, and so on.

SUMMARY OF THE INVENTION

The invention is, consequently, intended to propose a method of drivingthe gear of a vehicle with automatic transmission, making it possible toavoid the pumping phenomenon efficiently, regardless of the ratioengaged and the number of gear ratios.

Another object of the invention is to propose a method making possible aless erratic determination of the pumping risk, so as to optimizeoperation of the automatic transmission.

For that purpose, the invention concerns a method of elimination of thephenomenon of pumping of a motor vehicle with automatic transmission,characterized in that it includes the stages consisting of:

determining the weight of the vehicle, by using the measured speed ofthe vehicle, the current transmission ratio, the engine speed and theangle of opening of the engine throttle valve;

determining from the weight of the vehicle the acceleration that thevehicle would experience on the higher ratio;

determining the sum of the resistant forces applied to the vehicle;

from the information on acceleration and resistant forces, determiningthe possibility of having a pumping phenomenon on the higher ratio,called "pumping risk;"

from the "pumping risk" information, elaborating a signal preventingshift from the higher ratio, intended to be applied to the transmissioncontrol system.

According to other characteristics of the method of the invention:

in order to determine the possibility of having a pumping phenomenon onthe higher ratio, a fuzzy logic technique is used, including the stagesconsisting of:

determining the degree of membership of potential acceleration on thehigher ratio in a negative fuzzy subsystem defined by a givenacceleration threshold;

determining the degree of membership of the resistant forces in apositive fuzzy subsystem defined by a lower threshold of resistantforces and by a higher threshold of resistant forces;

from the degrees of membership in the fuzzy subsystems, determining thepumping risk on the higher ratio as being the minimum value of torque ofthe degrees of membership;

the lower and higher thresholds of resistant forces and/or the thresholdof acceleration on the higher ratio are determined by an adjustment anddepend on the current ratio engaged;

determination of the weight of the vehicle includes the stagesconsisting of:

calculating the acceleration of the vehicle from the measured speed ofthe vehicle;

calculating the wheel torque from the angle of opening of the throttlevalve, engine speed and reduction ratio of the transmission on thecurrent ratio;

determining a series of p variations of acceleration and torque betweentwo given times;

calculating the weight of the vehicle by a technique of identificationof recursive least squares of the variations of acceleration and torque.

the stage of calculation of the weight of the vehicle includes a stageof calculation of a gross weight calculated for each variation ofacceleration and torque, followed by a stage of calculation of weight bycalculation of a recursive average from the successive gross weightinformation.

the stage of calculation of acceleration of the vehicle from themeasured speed of the vehicle includes the stages consisting of:

filtering the measured speed information by means of a first-orderdigital low-pass filter, so as to obtain filtered speed information;

calculating the numerical derivative of the filtered speed informationso as to obtain vehicle acceleration information;

filtering the vehicle acceleration information by means of a digitallow-pass filter, so as to obtain filtered acceleration information fromthe vehicle.

the stage of calculation of the wheel torque includes the stagesconsisting of:

calculating the wheel torque by multiplying the gear reduction ratio ofthe vehicle on the current ratio by the engine torque;

filtering the wheel torque by means of the low-pass filters so as toobtain wheel torque information in phase with the filtered accelerationinformation from the vehicle;

the series of p variations of acceleration and torque is calculatedbetween two times spaced by approximately 0.5 second to 2.5 seconds;

the recursive least squares of the variations of acceleration and torqueare calculated for variations of acceleration and torque obtained whenthe brakes of the vehicle are not activated, when the variation of angleof opening of the throttle valve between the given times is below apredetermined threshold, and when the products of the variations oftorque by the variations of acceleration are higher than a predeterminedpositive threshold.

The invention also concerns a motor vehicle employing the method ofelimination of the pumping phenomenon, having the above characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by referring to the followingspecification, given by way of nonlimitative example and to the attacheddrawings, wherein:

FIG. 1 represents, in a graph of the angle of opening of the throttlevalve as a function of speed of the vehicle, a characteristic cycle ofthe pumping effect;

FIG. 2 represents a partial schematic view of a motor vehicle employingthe method of elimination of pumping on fuzzy logic according to theinvention;

FIG. 3 represents a general organization chart of the stages of themethod of elimination of pumping according to the invention;

FIG. 4 represents a graph of the function of membership of accelerationon the higher ratio γ(N+1) in the negative fuzzy subsystem;

FIG. 5 represents a graph of membership of the resistant forceF_(resistant) in the positive fuzzy subsystem;

FIG. 6 represents an organization chart of the stages of the method ofdetermination of weight of the vehicle.

DISCUSSION OF THE PREFERRED EMBODIMENTS

Reference is made to FIG. 1. The standard cycle of a pumping phenomenonhas been represented on this figure in a graph representing the angleα_(pap) [α_(throttle) valve ] of opening of the throttle valve as afunction of speed of the vehicle. That figure shows two curves 1 and 2of change of gear ratios of the vehicle, from ratio N to ratio N-1(curve 1) and from ratio N to ratio N+1 (curve 2) respectively, and atypical ABCD cycle 3 characteristic of the pumping phenomenon.

Starting from an operating point A corresponding to a gear ratio N, thedriver judges that the speed of the vehicle is high enough and lifts hisfoot from the accelerator, which diminishes the angle α_(pap) andcorresponds to the shift to point B of the cycle. On doing so, the cyclecrosses curve 2 and, consequently, the higher ratio N+1 is engaged; forexample, the fourth gear is engaged if the third was engaged. If thedriver can maintain the speed of the vehicle on this new ratio, there isno particular problem.

On the other hand, when the sum of the resistant forces applied to thevehicle is relatively high, the vehicle cannot maintain its speed onratio N+1. The speed diminishes, and when point C is reached, the driverreaccelerates. The angle α_(pap) widens, and the operating point passesto point D of the cycle. On doing so, the cycle crosses curve 1, so thatratio N-1 is engaged.

The resulting acceleration is then expressed by an increase of speed, sothat point A is reached again. That ABCD cycle characterizes pumping andgives rise to an uncomfortable and inefficient drive in a vehicle withautomatic transmission.

To remedy that problem, the invention provides a method of eliminationof pumping, depicted in FIG. 2 in conjunction with the correspondingfunctional elements of a motor vehicle. That method employs theelaboration by functional block 4, and according to a method indicatedin FIG. 3 and detailed below, of a variable 5 preventing shift to thehigher ratio, which is used by a functional block 6 representing thegear control unit, which decides the ratio N to be applied to theautomatic transmission (not represented). Functional block 6 integratesa control logic by itself known, which receives binary type information(0 or 1) preventing or allowing the shift to the higher ratio, thatinformation being managed by functional block 6 for engagement of thegears.

Functional block 4, which is an electronic logic system, theconstruction of which is evident simply from its functions, is a blockwhich generates the information preventing shift 5 from informationemanating from sensors 7, 8, 9, 10 associated with the vehicle, thosesensors comprising a speed sensor indicated by 7 and supplying themeasured speed of the vehicle, called V_(mes) [V_(measured) ], a sensor8 measuring the angle of opening α_(pap) of the throttle valve of thevehicle, a sensor 9 measuring the rotary speed of the engine, calledN_(mot) [N_(engine) ], and a braking sensor 10 indicating in binaryfashion whether the driver is braking or not at the time considered.Block 4 further receives from block 6 information indicating the ratio Napplied to the automatic transmission.

FIG. 3 details the mode of elaboration by block 4 of FIG. 2 of thevariable preventing shift to the higher ratio. The different blocksrepresented correspond to stages of the method according to theinvention, but it can be noted that they may also represent thecalculation blocks of a system capable of using the method. Thosecalculation blocks can easily be constructed by the expert from theirfunctions described here. Consequently, the calculation blocks will notbe described in detail.

The first stage consists of determining, in block 11, the weight M ofthe vehicle, that information then being transmitted to block 12. Thelatter determines the acceleration γ(N+1) that the vehicle would undergoon the higher ratio N+1, that acceleration being determined, notably,from the weight M of the vehicle, the source of which will be explainedin connection with FIG. 6. Block 12 also determines an evaluation of thesum of the resistant forces F_(resistant).

With these two pieces of information γ(N+1) and F_(resistant), block 13determines the risk or possibility of pumping that might exist on thehigher ratio N+1, called "pumping risk" and the value of which rangesbetween 0 and 1, where 0 corresponds to the absence of pumping and where"1" corresponds to a certain probability.

Block 14 determines the shift prevention signal, which bars change toany higher ratio.

The invention provides for determination of the weight M of the vehicleto be made according to a method whose stages are depicted in FIG. 6. Inthat figure the speed V_(mes) of the vehicle, as measured by sensor 7,is filtered in filtering block 20a, employing a first-order low-passdigital filter, which delivers filtered speed information V_(fil)calculated from the speed V_(mes) by means of the following recursionformula:

    V.sub.fil (t)=K.V.sub.fil (t-Te)+(1-K).V.sub.mes (t),      (1)

in which t is the current sampling time, t-Te the previous samplingtime, Te the sampling period, and K the filtering constant of the filtercalculated according to the following expression:

    K=exp.(-2π.fc.Te),                                      (2)

where fc is the cutoff frequency of the filter and exp designates theexponential function. Block 21 processes the filtered speed informationV_(fil) so as to calculate the acceleration γ_(mes) of the vehicle bymeans of the standard numerical derivation formula:

    γ.sub.mes (t)=[V.sub.fil (t)-V.sub.fil (t-Te)]/Te    (3).

That information γ_(mes) representing the acceleration of the vehicle isthen filtered by means of filtering block 20b, which has the samefunction as block 20a, so as to deliver the information γ_(fil)representing the filtered acceleration of the vehicle. Block 22determines from information α_(pap) (angle of opening of the throttlevalves) and N_(mot) (rotary speed of engine) a value representing theengine torque, which can be obtained, for example, by a readinginterpolated in a chart. For reasons of good convergence of the methodof calculation of weight, it is necessary for engine torque precision tobe good.

Block 23 makes it possible to determine the wheel torque of the vehiclefrom the engine torque and gear ratio N by means of formula:

    C.sub.roue (N)=rap(N).C.sub.mot [C.sub.wheel (N)=rap(N).C.sub.engine ](4)

in which rap(N) is the gear reduction ratio on ratio N and C_(mot) theengine torque.

This wheel torque value is filtered two consecutive times by filteringblock 20c, which delivers information C_(roue).fil [C_(wheel).fil ].

Blocks 20c and 20d have the same function as block 20a and are mainlyintended to bring the two pieces of information γ_(fil) and C_(roue).filinto phase for the treatments to be applied to them.

Block 24 has the function, among others, of calculating the variationsof torque and acceleration noted as ΔC and Δγ, which will feed the block25 calculating the weight of the vehicle M by an identificationtechnique of recursive least squares. In fact, between two times t₁ andt₂ close enough for the variations of torque and acceleration to besignificant and slightly distant enough for little or no variation ofthe resistant forces, the relation joining ΔC to Δγ is:

    M.Δγ=ΔC/radius,                          (5)

where radius designates the wheel radius.

The method of recursive least squares used in block 25 makes it possibleto calculate from a set of P measurements of variations of torque andacceleration ΔC(i) and Δγ(i), i being the index of measurement, todetermine the parameter M which minimizes the quadratic criterion:

    J=Σ(i=1 at i=p) (M.Δγ(i)-ΔC(i)/radius).sup.2 (6).

This method of identification is described, for example, in the workentitled "Identification et commande des systemes" [Systemidentification and control] by loan Dore Landau, Editions Hermes, 1988,pages 177 to 208. Block 24 has the function of determining the "good"variations of torque and acceleration, so that a good torque (Δγ, ΔC) isdefined by the following conditions (7), placing:

    Δγ=γ(t.sub.2)-γ(t.sub.1) between two times t.sub.2 and t.sub.1

    ΔC=C.sub.roue (t.sub.2)-C.sub.roue (t.sub.1)

    Δγ. ΔC>SC.sub.γ >0                 (7)

and

    0.5 s<t.sub.2 -t.sub.1 <2.5 s

and brake=0

and |d(α_(pap))dt|_(t1).t2 <S_(d)α

The above conditions signify:

that a pair of measurements ΔC and Δγ is judged good when the productΔC.Δγ is higher than a threshold called positive SCγ, which makes itpossible to ensure that the variations of torque and acceleration are ofthe same sign and correspond to a minimal "excitation" sufficient foridentification;

that the calculations of variations ΔC and Δγ correspond to points atleast 0.5 s away in order to observe significant variations and at most2.5 s away for the variations of resistant forces not to influence theidentification procedure;

that the brakes are not activated, for the brakes would create unknownand variable resistant forces;

that the variation of the angle of opening of the throttle valve attimes t₁ and t₂ is slight (that is, that the derivative of α_(pap) (t)is less than a threshold Sdα₁ for the calculations of engine torque fromcharts at times t₁ and t₂ will be correct only if they correspond tostable points.

Block 25 has the function of calculating the weight of the vehicle,called M_(brute) [M_(gross)) by an identification technique of recursiveleast squares with constant gain, described in the above-mentioned workby Landau, the procedure of which, applied to the present case, is asfollows:

Let M'(t-1) be the estimated weight at the previous time of samplingt-1. The standard deviation, called ε_(norm), is calculated from a newpair of points of measurement of variations of torque and acceleration(ΔC,Δγ), using the expression:

    ε.sub.norm =[(ΔC/radius)-M'(t-1).Δγ]/(1+f.Δγ.sup.2), (8)

expression in which f is the adaptation gain, which is constant.

The calculation of weight at the current sampling time t results thenfrom the following expression (9):

    M.sub.brute =M'(t)=M'(t-1)+f.Δγ.ε.sub.norm (9).

Block 25, which delivers information M_(brute), is called every timeinformation (ΔC,Δγ) can be delivered by block 24.

Block 26 carries out averaging (which is not temporal) every time newinformation M_(brute) is delivered by block 25, which is at the rate ofthe flow of information from block 24. That block 26 delivers theinformation called M (average weight) which is calculated from the grossweight M_(brute) coming from block 25 thanks to expression (10):

    M(t)=1/(Nb-pt+1).[Nb-pt.M(t-1)+M.sub.brute ],              (10)

expression in which Nb-pt is the number of times new informationM_(brute) is available, and which is incremented by 1 on each call.M(t-1) is the average weight at the previous call time t-1, and M(t) isthe average weight at the current call time t.

This determination of weight M of the vehicle is used in block 12 ofFIG. 3, notably, to determine the acceleration the vehicle would have onratio N+1.

In block 12 of FIG. 3 this acceleration, called γ(N+1), as well as theresistant force called F_(resistant), are determined as follows:

    γ(N+1)=γ.sub.mes +[C.sub.roue (N+1)-C.sub.roue (N)/(radius.M) (11)

and

    F.sub.resistant =γ.sub.nom (α.sub.pap, V.sub.mes, N, N.sub.mot)-γ.sub.mes,                               (12)

in which expressions:

γ_(mes) is the real acceleration of the vehicle, calculated from thespeed of the vehicle by a filtering and derivation procedure analogousto that described concerning blocks 60 and 21 of FIG. 6:

C_(roue) (N) and C_(roue) (N+1) are respectively the wheel torques thatthe vehicle presents on ratio N and would have on ratio N+1. C_(roue)(N) is calculated by a procedure identical to that described in blocks22, 23 and 20c of FIG. 6. C_(roue) (N+1) is calculated in a manneranalogous to C_(roue) (N), being careful to calculate the speed theengine would have on ratio N+1:N_(mot) (N+1)=rap(N+1).V_(mes) /radius,which serves to determine the engine torque C_(mot) (N+1) the enginewould have on ratio N+1. The wheel torque on ratio N+1 is then deducedfrom the expression:

    C.sub.roue (N+1)=C.sub.mes (N+1).rap(N+1),                 (13)

rap(N+1) being the reduction ratio on ratio N+1.

Let M be the weight of the vehicle, as calculated in block 11 of FIG. 3,"radius" the radius of the wheels of the vehicle and γ_(nom) (α_(pap),V_(mes), N, N_(mot)) the nominal acceleration to which the vehicle wouldbe subject if it were running on flat terrain, without wind and with astandard weight empty. The nominal acceleration is calculated by meansof the following expression (14)

    γ.sub.non =C.sub.roue (N)/radius.M.sub.avide -T.sub.aero /M.sub.avide -T.sub.rout M.sub.avide                                   (14)

in which:

M_(avide) is the weight of the vehicle empty

T_(aero) is the aerodynamic drag:

T_(aero) =1/2.ρ.Scx.V² _(mes), ρ being the air density and Scx the airpenetration coefficient of the vehicle;

T_(roul) is the rolling drag: T_(roul) =M_(avide).g.kr, where g is theacceleration due to gravity (g=9.81 m/s²) and kr the rolling resistancecoefficient.

The two pieces of information γ(N+1) and F_(resistant), calculated inblock 12 of FIG. 3, make it possible, on the one hand, to predictwhether the acceleration on ratio N+1 can be negative and, on the other,to verify whether the vehicle is subjected to resistant forces. Thosetwo pieces of information are, consequently, processed in block 13 ofFIG. 3 by a so-called fuzzy logic technique, in order to determine thepumping risk that would exist if the gear control unit (block 32 of FIG.2) decided to change the higher ratio N+1, which is called pumping risk.

According to this invention, one determines the degree of membership ofγ(N+1) in the negative γ(N+1) fuzzy subsystem represented in FIG. 4, inwhich S.sub.γ is a threshold determined by the adjuster, and which canbe a function of the ratio engaged. That degree of membership is calledμ.sub.γ.

One also determines the degree of membership, called μ_(Fr), ofF_(resistant) in the positive F_(resistant) fuzzy subsystem in FIG. 5,in which the thresholds S_(r1) and S_(r2) are to be determined by theadjuster and can be a function of the ratio engaged.

Having determined the degrees of membership μ.sub.γ and μ_(Fr), thepumping risk is determined on the higher ratio as follows:

    pumping risk=Min(μ.sub.γ,μ.sub.Fr),            (15)

where Min designates the operator "minimum." That pumping risk,represented by the output of block 13, is processed in block 14 todetermine the shift prevention information, which is going to preventshift to the higher ratio in the gear control unit as follows: as soonas the pumping risk is higher than threshold S_(r1), the shiftprevention becomes active, that is, the shift prevention is at 1. Thatprevention is deactivated when the pumping risk is below S_(r2). In thatcase, the shift prevention signal is at 0. S_(r1) and S_(r2) are boththresholds determined by the adjuster to regulate the sensitivity of thepumping risk detection procedure.

It is evident from the foregoing that the invention responds perfectlyto the objectives set. It remedies the problems of the known methods andeliminates the pumping phenomenon, regardless of the number of gearratios and the ratio engaged. Furthermore, the fuzzy logic calculationsmake it possible to avoid any test of existence of all-or-nothingpumping, which is particularly apt to lead to erratic functioning of thegear.

By calculating the sum of the resistant forces applied to the vehicle,the method also makes it possible to verify whether the vehicle is underthe probable conditions of pumping.

Finally, the method according to the invention also makes possible amore precise calculation of the weight of the vehicle in dynamicfashion.

I claim:
 1. Method of elimination of the phenomenon of pumping of amotor vehicle with automatic transmission, by elaboration of a signalpreventing change from a higher ratio, intended to be applied to atransmission control system, characterized in that:the weight of thevehicle is determined by using the measured speed of the vehicle, thecurrent transmission ratio, the engine speed and the angle of opening ofthe engine throttle valve, and taking into account the state of thebrakes, the acceleration that the vehicle would experience on a highertransmission ratio is determined from the weight of the vehicle, the sumof the resistant forces applied to the vehicle is determined, thepossibility of having a pumping phenomenon on the higher ratiotransmission, called "pumping risk," is determined from the informationon acceleration and resistant forces, and the prevention signal iselaborated from the "pumping risk" information.
 2. Method according toclaim 1, characterized in that in order to determine the probability ofhaving a pumping phenomenon on the higher transmission ratio, a fuzzylogic technique is used, including the stages consisting of:determiningthe degree of membership of potential acceleration on the higher ratioin a negative fuzzy subsystem defined by a given acceleration threshold;determining the degree of membership of the resistant forces in apositive fuzzy subsystem defined by a lower threshold of resistantforces and by a higher threshold of resistant forces; from the degreesof membership in the fuzzy subsystems, determining the pumping risk onthe higher transmission ratio as being the minimum valueMin(μ.sub.γ,μ_(Fr)) of torque of the degrees of membership.
 3. Methodaccording to claim 2, characterized in that the determination of theweight of the vehicle includes the stages consisting of:calculating theacceleration of the vehicle from the measured speed of the vehicle;calculating the wheel torque from the angle of opening of the throttlevalve, engine speed and reduction ratio of the transmission of thecurrent ratio; determining a series of p variations of acceleration andtorque between two given times; calculating the weight of the vehicle bya technique of identification of recursive least squares of thevariations of acceleration and torque.
 4. Motor vehicle, characterizedin that it employs the method of elimination of the pumping phenomenonaccording to claim
 2. 5. Method according to claim 2, characterized inthat the lower threshold and higher threshold of resistant forces and/orthe threshold of acceleration on the higher ratio are determined by anadjustment and depend on the current ratio engaged.
 6. Method accordingto claim 5, characterized in that the determination of the weight of thevehicle includes the stages consisting of:calculating the accelerationof the vehicle from the measured speed of the vehicle; calculating thewheel torque from the angle of opening of the throttle valve, enginespeed and reduction ratio of the transmission of the current ratio;determining a series of p variations of acceleration and torque betweentwo given times; calculating the weight of the vehicle by a technique ofidentification of recursive least squares of the variations ofacceleration and torque.
 7. Motor vehicle, characterized in that itemploys the method of elimination of the pumping phenomenon according toclaim
 5. 8. Method according to claim 1, characterized in that thedetermination of the weight of the vehicle includes the stagesconsisting of:calculating the acceleration of the vehicle from themeasured speed of the vehicle; calculating the wheel torque from theangle of opening of the throttle valve engine speed and reduction ratioof the transmission on the current ratio; determining a series of ρvariations of acceleration and torque between two given times;calculating the weight of the vehicle by a technique of identificationof recursive least squares of the variations of acceleration and torque.9. Method according to claim 8, characterized in that the stage ofcalculation of the weight of the vehicle includes a stage of calculationof a gross weight calculated for each variation of acceleration andtorque, followed by a stage of calculation of weight by calculation of arecursive average from the successive gross weight information. 10.Method according to claim 8, characterized in that the recursive leastsquares of the variations of acceleration and torque are calculated forvariations of acceleration and torque obtained when the brakes of thevehicle are not activated, when the variation of angle of opening of thethrottle valve between the given times is below a given threshold, andwhen the products of the variations of torque by the variations ofacceleration are higher than a predetermined positive threshold. 11.Method according to claim 9, characterized in that the stage ofcalculation and acceleration of the vehicle from the measured speed ofthe vehicle includes the stages consisting of:filtering the measuredspeed information by means of a first-order digital low-pass filter, soas to obtain filtered speed information; calculating the numericalderivative of the filtered speed information so as to obtain vehicleacceleration information; filtering the vehicle acceleration informationby means of a digital low-pass filter, so as to obtain filteredacceleration information from the vehicle.
 12. Method of claim 9,characterized in that the stage of calculation of the wheel torqueincludes the stages consisting of:calculating the wheel torque bymultiplying the gear reduction ratio of the vehicle on the current ratioN by the engine torque; filtering the wheel torque by means of low-passfilters so as to obtain wheel torque information in phase with thefiltered acceleration information from the vehicle.
 13. Motor vehicle,characterized in that it employs the method of elimination of thepumping phenomenon according to claim
 9. 14. Method according to claim8, characterized in that the series of p variations of acceleration andtorque is calculated between two times spaced by approximately 0.5second to 2.5 seconds.
 15. Method according to claim 8, characterized inthat the stage of calculation of acceleration of the vehicle from themeasured speed of the vehicle includes the stages consistingof:filtering the measured speed information by means of a first-orderdigital low-pass filter, so as to obtain filtered speed information;calculating the numerical derivative of the filtered speed informationso as to obtain vehicle acceleration information; filtering the vehicleacceleration information by means of a digital low-pass filter, so as toobtain filtered acceleration information from the vehicle.
 16. Motorvehicle, characterized in that it employs the method of elimination ofthe pumping phenomenon according to claim
 15. 17. Motor vehicle,characterized in that it employs the method of elimination of thepumping phenomenon according to claim
 8. 18. Method according to claim8, characterized in that the stage of calculation of the wheel torqueincludes the stages consisting of:calculating the wheel torque bymultiplying the gear reduction ratio of the vehicle on the current ratioN by the engine torque; filtering the wheel torque by means of low-passfilters so as to obtain wheel torque information in phase with thefiltered acceleration information from the vehicle.
 19. Motor vehicle,characterized in that it employs the method of elimination of thepumping phenomenon according to claim
 18. 20. Motor vehicle,characterized in that it employs the method of elimination of thepumping phenomenon according to claim 1.